Up to now, a technique in which an acceleration sensor is buried in a back surface of a tire tread, and a road surface condition, for example, an asphalt road, a snowy road, or a frozen road, is estimated on the basis of a detection signal of the acceleration sensor has been proposed (for example, refer to Patent Literature 1). Specifically, in the case where the acceleration sensor is buried in the back surface of the tire tread, when a portion corresponding to a location in which the acceleration sensor is disposed in the tire tread contacts a road surface in association with the rotation of the tire, a vibration component corresponding to the road surface condition is superimposed on a detection signal of the acceleration sensor. For that reason, up to now, a frequency component of the vibration acquired when the tire portion corresponding to the portion in which the acceleration sensor is disposed in the tire tread contacts the road surface is analyzed to estimate the road surface condition.
In the above configuration, the frequency analysis of the detected signal increases power consumption. Further, additional electronic components are required for analyzing frequency components of the detected signal, and this will cause an increase in the cost.